Thermoset adhesive films

ABSTRACT

This invention is a film adhesive prepared from an adhesive composition comprising a polymer system, a film forming rubber compound, and curing agents for the polymeric system. The polymer system comprises a base polymer and electron donor and electron acceptor functionality.

This application is a continuation-in-part of Ser. No. 10/146,387 filed14 May 2002.

FIELD OF THE INVENTION

This invention relates to film adhesives, and particularly filmadhesives for use in semiconductor packaging.

BACKGROUND OF THE INVENTION

A common mode of electronics packaging involves affixing semiconductordevices onto substrates by means of an adhesive tape. Epoxy compoundsand resins currently are among the most commonly used materials forcurrent film based adhesive applications, such as die attach, in which asemiconductor die is attached to a substrate. In a typical embodiment, afilm-forming rubber polymer is blended with epoxy resins and a hardeningagent. These compositions can then be cured upon application of heat,which results in the development of a thermoset network. One drawback toepoxy adhesives is their ultimate latency. Typically, these materialsmust be stored at low temperature to avoid premature advancement of theadhesive. Moreover, the speed of cure for these compositions isrelatively slow making the die-attach operation the least efficient stepin the total assembly manufacturing process for wirebonded integratedcircuit packages. This creates a need for a film adhesive that can berapidly cured compared to the conventional thermoset film adhesives, andparticularly to films containing no epoxy.

SUMMARY OF THE INVENTION

This invention is a film adhesive prepared from an adhesive compositioncomprising a polymer system, a film forming rubber compound, and curingagents for the polymeric system. In a preferred embodiment the polymersystem contains no epoxy functionality. The polymer system comprises abase polymer and electron donor and electron acceptor functionality. Theelectron donor and electron acceptor functionality can be pendant fromthe base polymer, or can be interdispersed with the base polymer asindependent compounds. In some cases, the base polymer can function as afilm-forming rubber compound. The film can be prepared directly as amonolayer from the adhesive composition, or from coating the adhesivecomposition onto both sides of a thermal resistant tape substrate.

DETAILED DESCRIPTION OF THE INVENTION

The polymer system for preparing the film adhesives will contain a basepolymer (hereinafter “polymer” or “base polymer”) and electron donor andelectron acceptor functionality. The system can be segregated intoseveral classes: (1) an unsubstituted base polymer blended with anindependent electron donor compound and an independent electron acceptorcompound; (2) a base polymer substituted with pendant electron acceptorfunctionality, blended with an independent electron donor compound, andoptionally an independent electron acceptor compound; (3) a base polymersubstituted with pendant electron donor functionality, blended with anindependent electron acceptor compound and optionally an independentelectron donor compound; (4) a base polymer substituted with pendantelectron donor and electron acceptor functionality, or a combination ofa base polymer substituted with pendant electron donor functionality anda base polymer substituted with pendant electron acceptor functionality,optionally blended with an independent electron donor compound, or anindependent electron acceptor compound, or both. Preferably, there willbe a 1:1 molar ratio of electron donor to electron acceptor; however,the molar ratio can range from 0.01-1.0:1.0-0.01.

A suitable base polymer in the polymer system of the inventive filmadhesive is prepared from acrylic and/or vinyl monomers using standardpolymerization techniques. The acrylic monomers that may be used to formthe base polymer include α,β-unsaturated mono and dicarboxylic acidshaving three to five carbon atoms and acrylate ester monomers (alkylesters of acrylic and methacrylic acid in which the alkyl groups containone to fourteen carbon atoms). Examples are methyl acryate, methylmethacrylate, n-octyl acrylate, n-nonyl methacrylate, and theircorresponding branched isomers, such as, 2-ethylhexyl acrylate. Thevinyl monomers that may be used to form the base polymer include vinylesters, vinyl ethers, vinyl halides, vinylidene halides, and nitriles ofethylenically unsaturated hydrocarbons. Examples are vinyl acetate,acrylamide, 1-octyl acrylamide, acrylic acid, vinyl ethyl ether, vinylchloride, vinylidene chloride, acrylonitrile, maleic anhydride, andstyrene.

Another suitable base polymer in the polymer system of the inventivefilm adhesive is prepared from conjugated diene and/or vinyl monomersusing standard polymerization techniques. The conjugated diene monomersthat may be used to form the polymer base includebutadiene-1,3,2-chlorobutadiene-1,3, isoprene, piperylene and conjugatedhexadienes. The vinyl monomers that may be used to form the base polymerinclude styrene, α-methylstyrene, divinylbenzene, vinyl chloride, vinylacetate, vinylidene chloride, methyl methacrylate, ethyl acrylate,vinylpyridine, acrylonitrile, methacrylonitrile, methacrylic acid,itaconic acid and acrylic acid.

Alternatively, the base polymer can be purchased commercially. Suitablecommercially available polymers include acrylonitrile-butadiene rubbersfrom Zeon Chemicals and styrene-acrylic copolymers from Johnson Polymer.

In those systems in which the base polymer is substituted with electrondonor and/or electron acceptor functionality, the degree of substitutioncan be varied to suit the specific requirements for cross-link densityin the final applications. Suitable substitution levels range from 6 to500, preferably from 10 to 200.

The base polymer, whether substituted or unsubstituted will have amolecular weight range of 2,000 to 1,000,000. The glass transitiontemperature (Tg) will vary depending on the specific base polymer. Forexample, the Tg for butadiene polymers ranges from −100° C. to 25° C.,and for modified acrylic polymers, from 15° C. to 50° C.

Suitable electron donor functionality includes vinyl ether groups, vinylsilane groups, and carbon to carbon double bonds external to an aromaticring and conjugated with the unsaturation in the aromatic ring. Suitableelectron acceptor groups include maleimides, acrylates, fumarates andmaleates.

Examples of suitable starting materials for reacting with complementaryfunctionality on the base polymer in order to add the electron donor orelectron acceptor functionality pendant to the base polymer include: forelectron donor functionality, hydroxybutyl vinyl ether, cinnamylalcohol, 1,4 cyclohexane-dimethanol monovinyl ether,3-isopropenyl-α,α-dimethylbenzyl isocyanate, isoeugenol, and thederivatives of the aforementioned compounds; for electron acceptorfunctionality, dioctyl maleate, dibutyl maleate, dioctyl fumarate,dibutyl fumarate, N-(6-hydroxyhexyl) maleimide, 6-maleimidocaproic acid,and 3-maleimidopropionic acid.

Independent electron donor compounds for blending with the base polymerinclude compounds having at least two vinyl ether groups, or having atleast two carbon to carbon double bonds external to aromatic rings andconjugated with the unsaturation in the aromatic ring. Suitable divinylether examples include compounds such asbis[4-(vinyloxy)butyl]tere-phthalate, bis[4-(vinyloxy)butyl](4-methyl-1,3-phenylene)biscarbamate, bis[4-(vinyloxy) butyl]1,6-hexanediylbiscarbamate, 4-(vinyloxy)butyl stearate, andbis[4-(vinyloxy)butyl] (methylenedi-4,1-phenylene)biscarbamate (soldunder the trade name Vectomer from Morflex, Inc). Exemplary compoundshaving at least two carbon to carbon double bonds external to aromaticrings and conjugated with the unsaturation in the aromatic ring include:

-   -   the adduct of tricyclodecane-dimethanol and        3-isopropenyl-α,α-dimethylbenzyl isocyanate (m-TMI) having the        structure    -   the adduct of 2-hydroxyethyl disulfide and M-TMI having the        structure    -   the adduct of cyanurate/trifunctional isocyanate and cinnamyl        alcohol having the structure    -   the adduct of 1,3-propandiol and M-TMI having the structure    -   the adduct of 1,4-butanediol and M-TMI having the structure    -   and the adduct of cinnamyl alcohol and 1,6-diisocyanatohexane        having        These compounds can be prepared by standard synthetic methods        known to those skilled in the art without undue experimentation.

Independent electron acceptor compounds for blending with the basepolymer include resins having at least two intramolecular maleimide,acrylate, fumarate or maleate groups. Examples of bismaleimides include:N,N′-ethylene-bis-maleimide, N,N′-butylene-bis-maleimide,N,N′-phenylene-bis-maleimide, N,N′-hexamethylene-bis-maleimide, N,N′4,4′-diphenyl methane-bis-maleimide, N, N′4,4′-diphenylether-bis-maleimide, N,N′-4,4′-diphenyl sulfone-bis-maleimide,N,N′-4,4′-dicyclohexyl methane-bis-maleimide,N,N′-xylylene-bis-maleimide, N,N′-diphenyl cyclohexane-bis-maleimide andthe like.

Suitable film forming resins or compounds include acrylic polymers (soldunder the trade name TEISAN RESIN from Nagase ChemteX Corporation) andacrylonitrile-butadiene elastomers (sold under the trade name NIPOL fromZeon Chemicals). These materials, in general, will be present in theadhesive composition from which the film will be prepared, in an amountranging from 10% to 70%, preferably 15% to 50%, by weight of theadhesive formulation. Other levels may be suitable depending on the enduse application, and optimal levels can be determined without undueexperimentation on the part of the formulator.

Suitable curing agents for the polymer system are thermal initiators andphotoinitiators, present in an amount of 0.1% to 10%, preferably 0.1% to5.0%, by weight of the polymer system. Preferred thermal initiatorsinclude peroxides, such as butyl peroctoates and dicumyl peroxide, andazo compounds, such as 2,2′-azobis(2-methyl-propanenitrile) and2,2′-azobis(2-methyl-butanenitrile). A preferred series ofphotoinitiators is one sold under the trademark Irgacure by CibaSpecialty Chemicals. In some formulations, both thermal initiation andphotoinitiation may be desirable; for example, the curing process can bestarted by irradiation, and in a later processing step curing can becompleted by the application of heat to accomplish the thermal cure. Ingeneral, these compositions will cure within a temperature range of 70°C. to 250° C., and curing will be effected at a temperature within therange of ten seconds to three hours. The time and temperature curingprofile of each formulation will vary with the specific electron donorcompound and the other components of the formulation, but the parametersof a curing profile can be determined by a practitioner skilled in theart without undue experimentation.

In some cases, it may be an advantage to add an epoxy compound or resinto the adhesive composition. Suitable epoxy compounds or resins includebifunctional and polyfunctional epoxy resins such as bisphenol A-typeepoxy, cresol novolak epoxy, or phenol novolak epoxy. Another suitableepoxy resin is a multifunctional epoxy resin from Dainippon Ink andChemicals, Inc. (sold under the product number HP-7200). When added tothe formulation, the epoxy will be present in an amount up to 80% byweight.

If an epoxy compound is added, the formulation will need to contain acuring or hardening agent for the epoxy. Suitable curing agents includeamines, polyamides, acid anhydrides, polysulfides, trifluoroboron, andbisphenol A, bisphenol F and bisphenol S, which are compounds having atleast two phenolic hydroxyl groups in one molecule. A curing acceleratormay also be used in combination with the curing agent. Suitable curingaccelerators include imidazoles, such as 2-methylimidazole,2-ethyl-4-methylimidazole, 4-methyl-2-phenylimidazole, and1-cyanoethyl-2-phenylimidazolium trimellitate. The curing agents andaccelerators are used in standard amounts known to those skilled in theart.

Other materials, such as adhesion promoters (epoxides, silanes), dyes,pigments, and rheology modifiers, may be added as desired formodification of final properties. Such materials and the amounts neededare within the expertise of those skilled in the art.

Filler particles that enhance the mechanical, electrical conductivity,or thermal conductivity may also be added. Suitable conductive fillersare carbon black, graphite, gold, silver, copper, platinum, palladium,nickel, aluminum, silicon carbide, boron nitride, diamond, and alumina.Suitable nonconductive fillers are particles of vermiculite, mica,wollastonite, calcium carbonate, titania, sand, glass, fused silica,fumed silica, barium sulfate, and halogenated ethylene polymers, such astetrafluoroethylene, trifluoroethylene, vinylidene fluoride, vinylfluoride, vinylidene chloride, and vinyl chloride. When present, fillerswill be in amounts of 0.1% to 90%, preferably from 5% to 90%, by weightof the formulation.

POLYMER SYNTHETIC EXAMPLES Example 1

This example discloses a butadiene/acrylo-nitrile base polymercontaining pendant acrylate (electron acceptor) functionality.

where x=50, y=5, n=310, p=678, and q=59, based on GPC and NMR analysis(one skilled in the art will recognize that these values may varyslightly due to the polymeric character of the material).

Carboxylated butadiene/acrylonitrile polymer (50.6 g) (Nipol 1072 fromZeon Chemicals) was solvated in 4-methyl-2-pentanone (MIBK, 250 mL) in a500 mL four-necked flask equipped with a mechanical stirrer, condenserand drying tube. Glycidyl methacrylate (9.78 g) andtetrabutylphosphonium acetate solution (0.58 g) (TBPAAC, catalyst, 70%by weight of tetrabutylphosphonium acid acetate in methanol from MortonInternational, Inc.) were added to the mixture with stirring. Themixture was heated to 110° C. and held at that temperature forapproximately twelve hours. The final product has a viscosity of 4870mPa·s at ambient temperature and according to titration results of theresidual carboxylic acid of the modified Nipol rubber, the carboxylconversion is about 90%. According to GPC analysis, the weight averagemolecular weight and the number average molecular weight of the modifiedNipol polymer are 430,500 g/mol and 60,900 g/mol, respectively.

Example 2

This example discloses a butadiene/acrylonitrile base polymer withpendant styrenic (electron donor) functionality,

where x=56, y=16, n=401, p=877, and q=76 based on GPC and NMR analysis(one skilled in the art will recognize that these values may varyslightly due to the polymeric character of the material).

Carboxylated butadiene/acrylonitrile polymer (38.0 g) (Nipol 1072 fromZeon Chemicals) was solvated in 4-methyl-2-pentanone (MIBK, 255 mL) in a500 mL four-necked flask equipped with a mechanical stirrer, condenserand drying tube. Isoeugenol glycidyl ether (11.43 g) andtetrabutyl-phosphonium acetate solution (0.62 g) (TBPAAC, catalyst, 70%by wetight of tetrabutylphosphonium acid acetate in methanol from MortonInternational, Inc.) were added into the mixture with stirring. Themixture was heated to 110° C. and held at that temperature forapproximately fourteen hours. According to titration results of theresidual carboxylic acid of the modified Nipol rubber, the carboxylconversion is about 87%. The product was purified by precipitation inmethanol three times. According to GPC analysis, the weight averagemolecular weight and the number average molecular weight of the modifiedNipol polymer are 554,400 g/mol and 89,100 g/mol, respectively.

Example 3

This example discloses a butadiene/acrylonitrile base polymer withpendant styrenic (electron donor) functionality,

where x=49, y=7, n=310, p=739, and q=59 based on GPC and NMR analysis(one skilled in the art will recognize that these values may varyslightly due to the polymeric character of the material).

Carboxylated butadiene/acrylonitrile polymer (53.8 g) (Nipol 1072 fromZeon Chemicals) was solvated in 4-methyl-2-pentanone (MIBK, 360 mL) in a1 L four-necked flask equipped with a mechanical stirrer, condenser anddrying tube. Glycidyl N-(3-isopropenyl-α,α-dimethylbenzyl) carbamate(14.8 g) and tetrabutylphosphonium acetate solution (0.54 g) (TBPMC,catalyst) were added into the mixture with stirring. The mixture washeated to 105° C. and held at that temperature for approximately fifteenhours. The final product has a viscosity of 2000 mPa·s at ambienttemperature and according to titration results, the carboxyl conversionis about 88%. According to GPC analysis, the weight average molecularweight and the number average molecular weight of the modified Nipolpolymer are 666,000 g/mol and 75,600 g/mol, respectively.

Example 4

This example discloses a butadiene/acrylonitrile base polymer withpendant cinnamyl (electron donor) functionality,

A solution of carboxylated butadienelacrylonitrile polymer (one molarequivalent based on the carboxylic acid) in toluene is reacted withexcess thionyl chloride at 50° C. for approximately fourteen hours. Theexcess thionyl chloride and the solvent are removed under reducedpressure to afford the butadiene/acrylonitrile polymer with pendant acidchloride.

One molar equivalent of cinnamyl alcohol and one molar equivalent oftriethylamine are mixed in dry toluene at 0° C., to which is added thebutadiene/acrylonitrile polymer with pendant acid chloride dissolved indry toluene (one molar equivalent based on the acid chloride). Themixture is allowed to react overnight. The product is purified byprecipitation in methanol three times.

Example 5

This example discloses a butadiene/acrylonitrile base polymer withpendant cinnamyl (electron donor) functionality,

One molar equivalent of cinnamyl amine and one molar equivalent oftriethylamine are mixed in dry toluene at 0° C., to which is added thebutadiene/acrylonitrile polymer with pendant acid chloride dissolved indry toluene (one molar equivalent based on the acid chloride). Themixture is allowed to react overnight. The product is purified byprecipitation in methanol three times.

Example 6

This example discloses a butadiene/acrylonitrile base polymer withpendant styrenic (electron donor) functionality,

One molar equivalent of isoeugenol and one molar equivalent oftriethylamine are mixed in dry toluene at 0° C., to which is added thebutadiene/acrylonitrile polymer with pendant acid chloride dissolved indry toluene (one molar equivalent based on the acid chloride). Themixture is allowed to react overnight. The product is purified byprecipitation in methanol three times.

Example 7

This example discloses a butadiene/acrylonitrile base polymer withpendant styrenic (electron donor) functionality,

One molar equivalent of 4-vinyl benzyl amine and one molar equivalent oftriethylamine are mixed in dry toluene at 0° C., to which is added thebutadiene/acrylonitrile polymer with pendant acid chloride dissolved indry toluene (one molar equivalent based on the acid chloride). Themixture is allowed to react overnight. The product is purified byprecipitation in methanol three times.

Example 8

This example discloses a butadiene/acrylonitrile base polymer withpendant vinyl ether (electron donor) functionality,

One molar equivalent of 4-hydroxybutyl vinyl ether and one molarequivalent of triethylamine are mixed in dry toluene at 0° C., to whichis added the butadiene/acrylonitrile polymer with pendant acid chloridedissolved in dry toluene (one molar equivalent based on the acidchloride). The mixture is allowed to react overnight. The product ispurified by precipitation in methanol three times.

Example 9

This example discloses a butadiene/acrylonitrile base polymer withpendant vinyl ether (electron donor) functionality,

One molar equivalent of 2-aminoethyl vinyl ether and one molarequivalent of triethylamine are mixed in dry toluene at 0° C., to whichis added the butadiene/acrylonitrile polymer with pendant acid chloridedissolved in dry toluene (one molar equivalent based on the acidchloride). The mixture is allowed to react overnight. The product ispurified by precipitation in methanol three times.

Example 10

This example discloses a hydroxylated styrene/butadiene base polymerwith pendant styrenic (electron donor) functionality,

One molar equivalent (based on hydroxyl function) of hydroxylatedstyrene/butadiene polymer is solvated in dry toluene at 90° C. undernitrogen, followed by the addition of one molar equivalent of3-isopropenyl-α,α-dimethylbenzyl isocyanate (m-TMI) together with 0.07%of dibutyltin dilaurate (catalyst) based on the total amount ofreactants. The resulting mixture is heated for an additional twenty-fourhours under nitrogen. After removal of the solvent under reducedpressure, the product is obtained in almost quantitative yield.

Example 11

This example discloses a hydroxylated styrene/butadiene base polymerhaving pendant styrenic (electron donor) functionality,

One molar equivalent of butadiene/styrene polymer based on the 1,2-vinylbonds is solvated in dry toluene under nitrogen and 0.3 molar equivalentof 2-mercaptoethanol is added into the mixture, followed by heating to75° C. A solution of azodiisobutyronitrile (AIBN) in toluene is thenadded to the mixture. The mixture is stirred at 75° C. for 7 hours. Theproduct is purified by precipitation in methanol three times.

One molar equivalent (based on hydroxyl function) of hydroxylatedstyrene/butadiene polymer prepared as above is solvated in dry tolueneat 90° C. under nitrogen, followed by the addition of one molarequivalent of 3-isopropenyl-α,α-dimethylbenzyl isocyanate (m-TMI)together with 0.07% of dibutyltin dilaurate (catalyst) based on thetotal amount of reactants. The resulting mixture is heated for anadditional twenty-four hours under nitrogen. After removal of thesolvent under reduced pressure, the product is obtained in almostquantitative yield.

Example 12

This example discloses a hydroxylated styrene/butadiene base polymerhaving pendant maleimide (electron acceptor) functionality,

One molar equivalent (based on hydroxyl function) of hydroxylatedstyrene/butadiene polymer prepared as in Example 11 is solvated in drytoluene at 90° C. under nitrogen, followed by the addition of one molarequivalent of 6-maleimidocaproic acid in toluene. Catalytic amount ofsulfuric acid is then introduced into the mixture. The mixture is heatedto reflux and water generated during the reaction is removed byazeotrope. The reaction is run overnight. The product is purified byprecipitation in methanol three times.

Example 13

This example discloses a polybutadiene base polymer with pendantstyrenic (electron donor) functionality,

One molar equivalent (based on anhydride function) of polybutadieneadducted with maleic anhydride (trade name: Ricon 131 MA20, produced bySartomer Company) is solvated in acetone, followed by the dropwiseaddition of one molar equivalent of cinnamyl amine. The reaction mixtureis stirred for 6 hours. After acetone is removed by reduced pressure,the polymer is solvated in toluene and the product is purified byprecipitation in methanol three times.

Example 14

This example discloses a styrene/acrylic base polymer with pendantacrylate (electron acceptor) functionality.

where m=11 based on GPC and NMR analysis (one skilled in the art willrecognize that this value may vary slightly due to the polymericcharacter of the material).

In a 500 mL four-necked flask equipped with a mechanical stirrer,condenser, addition funnel and a N₂ inlet, was charged with 45.02 g of astyrene-acrylic polymer (Joncryl 587 from Johnson Polymer) in methylenechloride (100 mL). After the polymer was solvated under nitrogen at roomtemperature, the solution was cooled to 0° C. and 6.83 g oftriethylamine was added to the mixture. To this resulting mixture wasadded dropwise 6.11 g of acryloyl chloride. The mixture was allowed toreact for an additional 6 hours. After washing with aqueous solutionsseveral times until the aqueous phase is neutral, the resulting organiclayer was dried over Mg₂SO₄ and silica gel. After the solvents wereremoved under reduced pressure, a white solid was obtained.

Example 15

This example discloses a styrene/acrylic base polymer with pendantstyrenic (electron donor) functionality,

where m=11 based on GPC and NMR analysis (one skilled in the art willrecognize that this value may vary slightly due to the polymericcharacter of the material).

In a 1 L four-necked flask equipped with a mechanical stirrer,condenser, addition funnel and a N₂ inlet, was charged with 126.7 g of astyrene acrylic polymer (Joncryl 587 from Johnson Polymer) in methylethyl ketone (620 mL). After the polymer was solvated at the refluxingtemperature of the solvent under nitrogen, 40.58 g of3-isopropenyl-α,α-dimethylbenzyl isocyanate (m-TMI) was added to themixture together with 0.12 g of dibutyltin dilaurate (catalyst). Theresulting mixture was heated for an additional twenty-four hours undernitrogen. After removal of the solvent under reduced pressure, a whitesolid was obtained in almost quantitative yield. According to GPCanalysis, the weight average molecular weight and the number averagemolecular weight of the modified styrene-acrylic polymer are 15,600g/mol and 8,400 g/mol, respectively. According to DSC analysis, theglass transition temperature of the modified styrene-acrylic polymer isapproximately 40° C.

ADHESIVE FILM EXAMPLES Example 16

An adhesive film was prepared from a polymer system comprising anunsubstituted acrylic/rubber base polymer, an independent electronacceptor resin, an independent electron donor resin, and an epoxy resin,which components and parts by weight used are identified in Table 1. Thefilm formulation also contained a radical initiator, hardeners for theepoxy, a filler and adhesion promoters. TABLE 1 Component Chemical ClassParts or Function Source by wt. Base polymer SG-80DR 5 Acrylic rubberNagase ChemteX Corp. Electron acceptor Matrimid 5292A 3 BismaleimideCiba Specialty Chemicals Corporation Electron donor Adduct oftricyclodecane- 2.5 Structure I dimethanol/m-TMI Epoxy HP-7200H 3.5Dainippon Ink and Chemicals, Inc.

The electron donor had the following structure:

The film formulation was prepared by mixing the components in methylethyl ketone with stirring, followed by vacuum degassing. The varnishobtained was coated to a thickness of 2 mil onto a 5 mil thicksilicone-treated release-liner and then dried by heating at 100° C. for10 minutes to form a partially cured adhesive film with a thickness of 1mil.

Example 17

An adhesive film was prepared from a polymer system comprising apoly(butadiene) base polymer substituted with pendant electron acceptorfunctionality, an independent electron acceptor resin, an independentelectron donor resin, and an epoxy resin, which components and parts byweight used are identified in Table 2. The film formulation alsocontained a radical initiator, hardeners for the epoxy, and adhesionpromoters. TABLE 2 Component Chemical Class Parts or Function Source bywt. Butadiene base polymer Polymer from Example 1. 2 substituted withpendant electron acceptor functionality Electron acceptor Matrimid 5292A1 Bismaleimide Ciba Specialty Chemicals Corporation Electron donorAdduct of tricyclodecane- 2.5 Structure I dimethanol/m-TMI EpoxyHP-7200H 3.5 Dainippon Ink and Chemicals, Inc.

The film formulation was prepared by mixing the components in methylethyl ketone with stirring, followed by vacuum degassing. The varnishobtained was coated to a thickness of 2 mil onto a 5 mil thicksilicone-treated release-liner and then dried by heating at 100° C. for10 minutes to form a partially cured adhesive film with a thickness of 1mil.

Example 18

An adhesive film was prepared from a polymer system comprising astyrene/acrylic base polymer substituted with pendant electron donorfunctionality, an independent electron acceptor resin, an independentelectron donor resin, and an acrylonitrile/butadiene rubber, whichcomponents and parts by weight used are identified in Table 3. The filmformulation also contained a radical initiator and adhesion promoters.TABLE 3 Component Chemical Class Parts or Function Source by wt.Sytrene/acrylic base polymer Polymer from 2 substituted with pendantExample 15 electron donor functionality Electron acceptor Matrimid 5292A5 Bismaleimide Ciba Specialty Chemicals Corporation Electron donorAdduct of 1.75 Structure I tricyclodecane- dimethanol/m-TMIAcrylonitrile/butadiene Zeon Chemicals 4 rubber

The film formulation was prepared by mixing the components in methylethyl ketone with stirring, followed by vacuum degassing. The varnishobtained was coated to a thickness of 2 mil onto a 5 mil thicksilicone-treated release-liner and then dried by heating at 100° C. for10 minutes to form a partially cured adhesive film with a thickness of 1mil.

Example 19

An adhesive film was prepared from a polymer system comprising astyrene/acrylic base polymer substituted with pendant electron donorfunctionality, an acrylonitrile/butadiene base polymer substituted withpendant electron donor functionality, an independent electron acceptorresin, an independent electron donor resin, which components and partsby weight used are identified in Table 4. The film formulation alsocontained a radical initiator, filler, and adhesion promoters. TABLE 4Component Chemical Class Parts or Function Source by wt. Sytrene/acrylicbase polymer Polymer from Example 2 substituted with pendant 15 electrondonor functionality Acrylonitrile/butadiene base Polymer from Example 24 polymer substituted with pendant electron donor functionality Electronacceptor Matrimid 5292A 5 Bismaleimide Ciba Specialty ChemicalsCorporation Electron donor Adduct of 1.8 Structure I tricyclodecane-dimethanol/m-TMI

The film formulation was prepared by mixing the components in methylethyl ketone with stirring, followed by vacuum degassing. The varnishobtained was coated to a thickness of 2 mil onto a 5 mil thicksilicone-treated release-liner and then dried by heating at 100° C. for10 minutes to form a partially cured adhesive film with a thickness of 1mil.

Example 20

An adhesive film was prepared from a polymer system comprising aacrylonitrile/butadiene base polymer substituted with pendant electrondonor functionality, an independent electron acceptor resin, anindependent electron donor resin, and an epoxy, which components andparts by weight used are identified in Table 5. The film formulationalso contained a radical initiator, hardeners for the epoxy, filler, andadhesion promoters. TABLE 5 Component Chemical Class Parts or FunctionSource by wt. Acrylonitrile/butadiene base Polymer from Example 2 2.5polymer substituted with pendant electron donor functionality Electronacceptor Matrimid 5292A 3 Bismaleimide Ciba Specialty ChemicalsCorporation Electron donor Adduct of 2.5 Structure I tricyclodecane-dimethanol/m-TMI Epoxy HP-7200H 3.5 Dainippon Ink and Chemicals, Inc.

The film formulation was prepared by mixing the components in methylethyl ketone with stirring, followed by vacuum degassing. The varnishobtained was coated to a thickness of 2 mil onto a 5 mil thicksilicone-treated release-liner and then dried by heating at 100° C. for10 minutes to form a partially cured adhesive film with a thickness of 1mil.

Example 21

An adhesive film was prepared from a polymer system comprising aacrylonitrile/butadiene base polymer substituted with pendant electrondonor functionality, an independent electron acceptor resin, anindependent electron donor resin, and an epoxy, which components andparts by weight used are identified in Table 6. The film formulationalso contained a radical initiator, hardeners for the epoxy, filler, andadhesion promoters. TABLE 6 Component Chemical Class Parts or FunctionSource by wt. Acrylonitrile/butadiene base Polymer from Example 3 2.5polymer substituted with pendant electron donor functionality Electronacceptor Matrimid 5292A 3 Bismaleimide Ciba Specialty ChemicalsCorporation Electron donor Adduct of 2.5 Structure I tricyclodecane-dimethanol/m-TMI Epoxy HP-7200H 3.5 Dainippon Ink and Chemicals, Inc.

The film formulation was prepared by mixing the components in methylethyl ketone with stirring, followed by vacuum degassing. The varnishobtained was coated to a thickness of 2 mil onto a 5 mil thicksilicone-treated release-liner and then dried by heating at 100° C. for10 minutes to form a partially cured adhesive film with a thickness of 1mil.

Example 22

An adhesive film was prepared from a polymer system comprising anacrylonitrile/butadiene base polymer substituted with pendant electronacceptor functionality, a styrene/acrylic base polymer substituted withpendant electron donor functionality, an independent electron acceptorresin, an independent electron donor resin, which components and partsby weight used are identified in Table 7. The film formulation alsocontained a radical initiator. TABLE 7 Component Chemical Class Parts orFunction Source by wt. Acrylonitrile/butadiene base Polymer from Example1 2.5 polymer substituted with pendant electron donor functionalityStyrene/acrylic base polymer Polymer from Example 3 substituted withpendant 15 electron donor functionality Electron acceptor Matrimid 5292A5 Bismaleimide Ciba Specialty Chemicals Corporation Electron donorAdduct of 1.8 Structure I tricyclodecane- dimethanol/m-TMI

The film formulation was prepared by mixing the components in methylethyl ketone with stirring, followed by vacuum degassing. The varnishobtained was coated to a thickness of 2 mil onto a 5 mil thicksilicone-treated release-liner and then dried by heating at 100° C. for10 minutes to form a partially cured adhesive film with a thickness of 1mil.

COMPARATIVE ADHESIVE FILM EXAMPLE Example 23

This example discloses an adhesive film prepared with a polymeric systemcontaining an acrylonitrile/butadiene base polymer, and epoxy resin, andno electron donor nor electron acceptor functionality. The formulationalso contained a phenol novolak resin and curing agents. The formulationcomponents and parts by weight are disclosed in Table 8. TABLE 8Component Chemical Class Parts or Function Source by wt.Acrylonitrile/butadiene Nipol 1072 2.7 rubber Zeon Chemicals EpoxyHP-7200H 3.5 Dainippon Ink and Chemicals, Inc. Phenol Novolak resinHRJ-1166 1 Schenectady International Inc.

The film formulation was prepared by mixing the components in methylethyl ketone with stirring, followed by vacuum degassing. The varnishobtained was coated to a thickness of 2 mil onto a 5 mil thicksilicone-treated release-liner and then dried by heating at 100° C. for10 minutes to form a partially cured adhesive film with a thickness of 1mil.

PERFORMANCE EXAMPLES Example 24

A sample of each film produced in Examples 16-22 and Comparative Example23 was used to bond a 100 by 100 square mil silicon die to a PI flexsubstrate at 120° C. in 5 seconds and cured at 180° C. for one minute.The die shear strength of these bare packages was measured at 180° C. ona Dage Series 4000 Bondtester.

The results are disclosed in Table 9 and demonstrate that the inventivefilms have superior adhesive strength. TABLE 9 DIE SHEAR STRENGTH in KgForce @ 180° C. Cure condition 180° C./1 min Die shear strength measure180° C. temperature Example 16 1.86 Example 17 0.90 Example 18 2.22Example 19 1.93 Example 20 2.78 Example 21 2.80 Example 22 3.00Comparative Example 23 0.26

In a particular embodiment, the film forming polymers will be based onrubbery polymers having a weight average molecular weight (Mw) withinthe range of 300,000 to 1,500,000, and will be prepared from acrylic,vinyl, or conjugated diene monomers. These polymers will be the base foran electron donor/electron acceptor adhesive system, by which it ismeant that some of the compounds in the system will be electron donorsand some will be electron acceptors. In general, electron donor refersto an olefin compound that contains a carbon to carbon double bond withan electron-donating group, for example, vinyl ethers and compoundscontaining a carbon to carbon double bond attached to an aromatic ringand conjugated with the unsaturation in the ring; electron acceptorrefers to an olefin compound that contains a carbon to carbon doublebond with an electron-withdrawing group, for example, fumarates,maleates, acrylates, and maleimides. Specific compounds are disclosedearlier in this specification.

The base rubbery polymer will be chosen from polymers containing noelectron donor or acceptor functionality; polymers substituted withpendant electron donor functionality; polymers substituted with pendantelectron acceptor functionality; polymers substituted with both electrondonor and electron acceptor functionality; and a combination ofpolymers, one or more substituted with electron donor functionality andone or more substituted with electron acceptor functionality. In thecase in which the rubbery polymers have no electron donor or acceptorfunctionality, the adhesive system will contain independent compoundshaving electron donor functionality and electron acceptor functionality.In the case in which the rubbery polymers have either electron donor orelectron acceptor functionality, the adhesive system will containindependent compounds having electron acceptor functionality or electrondonor functionality, respectively, in order to form a complete electrondonor/electron acceptor system. It is optional to add additionalelectron donor or electron acceptor functionality to the adhesivesystems.

The prepared films of this invention are suitably used for attachingsemiconductor chips to substrates and for this purpose can be curedwithin two minutes at a temperature or temperature range below 300° C.

As would be understood by those skilled in the art, when the electrondonor and electron acceptor functionality is added as independentcompounds or polymers, those materials preferably should be compatiblewith the rubbery polymer. Compatible in this sense means that thecompounds are capable of forming a homogenous intimate mixture withoutseparation from the rubbery polymer into two or more phases during filmpreparation and after curing.

Example 25

Seven film adhesives, identified as Examples 25 A through G, wereprepared from various rubbery polymers and independent electron donorand electron acceptor compounds. The electron donor compound used hadtwo end styrenic functionalities and a dicyclopentadiene backbone. Theelectron acceptor compound used was a bismaleimide sold under thetradename Anilix-MI. The rubbery polymers used in the adhesiveformulation are indicated in Table 10 as polymers H through N and werethe following:

-   -   H: nitrile-butadiene rubber (Nipol 1072J, Zeon);    -   I: proprietary carboxyl terminated nitrile butadiene and epoxy        adduct;    -   J: proprietary carboxyl terminated nitrile butadiene and epoxy        adduct;    -   K: proprietary carboxyl terminated nitrile butadiene and epoxy        adduct;    -   L: acrylic rubber (Nagase, SG-8H DR)    -   M: acrylic rubber (Nagase, SG-P3 DR)    -   N: vinyl terminated nitrile butadiene (Hycarl300x43, Noveon)

The compositions, including the weight average molecular weight andglass transition temperature (Tg) of the rubbery polymers are recordedin Table 10. The components of the film adhesives were blended withmethyl ethyl ketone (solvent) and coated onto a release liner to athickness of approximately 25 μm. The solvent was evaporated off at atemperature of 99° C. for three minutes, and then the adhesive onrelease liner was passed through a roll laminator. Examples 25A, B, C,D, and G were rolled at 93° C.; Examples 25E and F were rolled at 140°C. Each adhesive (on release liner) was applied to a substrate with theadhesive contacting the substrate. The release liner was removed and asilicon chip contacted with the adhesive with temperature and pressure;Examples 25A, B, C, D, and G were contacted at 120° C. and 2 kgpressure; Examples 25E and F were contacted at 170° C. and 2 kgpressure. Die shear strength (DSS) was tested at 245° C. after 180° C.and one minute cure. Commercially acceptable die shear strengthspreferably are greater than 3.0. The Examples show that high molecularweight rubbery polymers are needed in order to obtain acceptable dieshear strengths. TABLE 10 Composition in Parts by Weight and Die ShearStrength of Film Adhesives Containing Rubbery Polymers Mw in Tg Ex Ex ExEx Ex Ex Ex Polymer 000 ° C. 25A 25B 25C 25D 25E 25F 25G H 320 −22 7.00I 85 −9 7.00 J 32 −15 7.00 K 15 40 7.00 L 350 0 7.00 M 1000 0 7.00 N 13−45 7.00 Electron 3.00 3.00 3.00 3.00 3.00 3.00 3.00 Donor Electron 5.005.00 5.00 5.00 5.00 5.00 5.00 Accep- tor Perox- 0.60 0.60 0.60 0.60 0.600.60 0.60 ide Total 15.60 15.60 15.60 15.60 15.60 15.60 15.60 solids ppwDSS 3.3 2.2 1.5 0.9 4.9 3.5 1.6

1. A film adhesive prepared from materials comprising (i) a rubberypolymer prepared from acrylic, vinyl, or conjugated diene monomers,containing no electron donor or acceptor functionality, and having aweight average molecular weight in the range of 300,000 to 1,500,000;(ii) an independent electron donor compound selected from the groupconsisting of vinyl ethers and compounds containing a carbon to carbondouble bond attached to an aromatic ring and conjugated with theunsaturation in the ring; (iii) an independent electron acceptorcompound; and (iv) a free radical initiator; characterized in that thefilm adhesive can be cured within two minutes at a temperature below300° C.
 2. The film adhesive according to claim 1 in which the rubberypolymer (i) is an acrylic polymer, a styrene-acrylic copolymer, or aacrylonitrile-butadiene copolymer.
 3. The film adhesive according toclaim 1 in which the independent electron donor compound (ii) is a vinylether selected from the group consisting ofbis[4-(vinyloxy)butyl]terephthalate, bis[4(vinyloxy)butyl](4-methyl-1,3-phenylene)-biscarbamate, bis[4-(vinyloxy) butyl]1,6-hexanediylbiscarbamate, 4-(vinyloxy)-butyl stearate, andbis[4-(vinyloxy) butyl] (methylenedi-4,1-phenylene)-biscarbamate.
 4. Thefilm adhesive according to claim 1 in which the independent electrondonor compound (ii) is a compound containing a carbon to carbon doublebond attached to an aromatic ring and conjugated with the unsaturationin the ring and are selected from the group consisting of:


5. The film adhesive according to claim 1 in which the independentelectron acceptor compound (iii) is selected from the group consistingof fumarates, maleates, acrylates, and maleimides.
 6. The film adhesiveaccording to claim 5 in which the independent electron acceptor compound(iii) is a bismaleimide selected from the group consisting ofN,N′-ethylene-bis-maleimide, N,N′-butylene-bis-maleimide,N,N′-phenylene-bis-maleimide, N,N′-hexamethylene-bis-maleimide,N,N′-4,4′-diphenyl methane-bis-maleimide, N,N′-4,4′-diphenylether-bis-maleimide, N,N′-4,4′-diphenyl sulfone-bis-maleimide,N,N′-4,4′-dicyclohexyl methane-bis-maleimide,N,N′-xylylene-bis-maleimide, and N,N′-diphenylcyclohexane-bis-maleimide.
 7. A film adhesive prepared from (i) arubbery polymer prepared from acrylic, vinyl, or conjugated dienemonomers, substituted with pendant electron acceptor functionality, andhaving a weight average molecular weight in the range of 300,000 to1,500,000, (ii) an independent electron donor compound selected from thegroup consisting of vinyl ethers and compounds containing a carbon tocarbon double bond attached to an aromatic ring and conjugated with theunsaturation in the ring; (iii) optionally, an independent electronacceptor compound; (iv) a free radical initiator; characterized in thatthe film adhesive can be cured within two minutes at a temperature below300° C.
 8. The film adhesive according to claim 7 in which the rubberypolymer (i) is an acrylic, styrene-acrylic copolymer, or aacrylonitrile-butadiene copolymer.
 9. The film adhesive according toclaim 7 in which the independent electron donor compound (ii) is a vinylether selected from the group consisting ofbis[4-(vinyloxy)butyl]terephthalate, bis[4(vinyloxy)butyl](4-methyl-1,3-phenylene)-biscarbamate, bis[4-(vinyloxy) butyl]1,6-hexanediylbiscarbamate, 4-(vinyloxy)-butyl stearate, andbis[4-(vinyloxy) butyl] (methylenedi-4,1-phenylene)-biscarbamate. 10.The film adhesive according to claim 7 in which the independent electrondonor compound (ii) is a compound containing a carbon to carbon doublebond attached to an aromatic ring and conjugated with the unsaturationin the ring and are selected from the group consisting of:


11. The film adhesive according to claim 7 in which the independentelectron acceptor compound (iii) is selected from the group consistingof fumarates, maleates, acrylates, and maleimides.
 12. The film adhesiveaccording to claim 7 in which the independent electron acceptor compound(iii) is a bismaleimide selected from the group consisting ofN,N′-ethylene-bis-maleimide, N,N′-butylene-bis-maleimide,N,N′-phenylene-bis-maleimide, N,N′-4,4′-diphenyl ether-bis-maleimide,N,N′-4,4′-diphenyl sulfone-bis-maleimide, N,N′-4,4′-dicyclohexylmethane-bis-maleimide, N,N′-xylylene-bis-maleimide, and N,N′-diphenylcyclohexane-bis-maleimide.
 13. A film adhesive prepared from (i) arubbery polymer prepared from acrylic, vinyl, or conjugated dienemonomers, substituted with pendant electron donor functionality, andhaving a weight average molecular weight in the range of 300,000 to1,500,000, (ii) an independent electron acceptor compound; (iii)optionally, an independent electron donor compound selected from thegroup consisting of vinyl ethers and compounds containing a carbon tocarbon double bond attached to an aromatic ring and conjugated with theunsaturation in the ring; and (iv) a free radical initiator;characterized in that the film adhesive can be cured within two minutesat a temperature below 300° C.
 14. The film adhesive according to claim13 in which the rubbery polymer (i) is an acrylic, styrene-acryliccopolymer, or a acrylonitrile-butadiene copolymer.
 15. The film adhesiveaccording to claim 15 in which the independent electron acceptorcompound (ii) is selected from the group consisting of fumarates,maleates, acrylates, and maleimides.
 16. The film adhesive according toclaim 13 in which the independent electron acceptor compound (ii) is abismaleimide selected from the group consisting ofN,N′-ethylene-bis-maleimide, N,N′-butylene-bis-maleimide,N,N′-phenylene-bis-maleimide, N,N′-hexamethylene-bis-maleimide,N,N′-4,4′-diphenyl methane-bis-maleimide, N,N′-4,4′-diphenylether-bis-maleimide, N,N′-4,4′-diphenyl sulfone-bis-maleimide,N,N′4,4′-dicyclohexyl methane-bis-maleimide,N,N′-xylylene-bis-maleimide, and N,N′-diphenylcyclohexane-bis-maleimide.
 17. The film adhesive according to claim 13in which the independent electron donor compound (iii) is a vinyl etherselected from the group consisting ofbis[4-(vinyloxy)butyl]terephthalate, bis[4(vinyloxy)butyl](4-methyl-1,3-phenylene)-biscarbamate, bis[4-(vinyloxy) butyl]1,6-hexanediylbiscarbamate, 4-(vinyloxy)-butyl stearate, andbis[4-(vinyloxy) butyl] (methylenedi-4,1-phenylene)-biscarbamate. 18.The film adhesive according to claim 13 in which the independentelectron donor compound (iii) is a compound containing a carbon tocarbon double bond attached to an aromatic ring and conjugated with theunsaturation in the ring and are selected from the group consisting of:


19. A rubbery film adhesive prepared from (i) a rubbery polymer preparedfrom acrylic, vinyl, or conjugated diene monomers, substituted withpendant electron donor and pendant electron acceptor functionality, andhaving a weight average molecular weight in the range of 300,000 to1,500,000, or (ii) a combination of (a) a rubbery polymer prepared fromacrylic, vinyl, or conjugated diene monomers, substituted with pendantelectron donor functionality and having a weight average molecularweight in the range of 300,000 to 1,500,000, and (b) a rubbery polymerprepared from acrylic, vinyl, or conjugated diene monomers, substitutedwith pendant electron acceptor functionality and having a weight averagemolecular weight in the range of 300,000 to 1,500,000; (iii) optionally,an independent electron donor compound selected from the groupconsisting of vinyl ethers and compounds containing a carbon to carbondouble bond attached to an aromatic ring and conjugated with theunsaturation in the ring; (iv) optionally, an independent electronacceptor compound; and (v) a free radial initiator; characterized inthat the film adhesive can be cured within two minutes at a temperaturebelow 300° C.
 20. The film adhesive according to claim 19 in which therubbery polymers of (i) and (ii) are acrylics, styrene-acryliccopolymers, or acrylonitrile-butadiene copolymers, or combinations ofthose.
 21. The film adhesive according to claim 19 in which independentelectron donor compound (ii) is a vinyl ether selected from the groupconsisting of bis[4-(vinyloxy)butyl]terephthalate, bis[4(vinyloxy)butyl](4-methyl-1,3-phenylene)-biscarbamate, bis[4-(vinyloxy) butyl]1,6-hexanediylbiscarbamate, 4-(vinyloxy)-butyl stearate, andbis[4-(vinyloxy) butyl] (methylenedi-4,1-phenylene)-biscarbamate. 22.The film adhesive according to claim 19 in which the independentelectron donor compound (ii) is a compound containing a carbon to carbondouble bond attached to an aromatic ring and conjugated with theunsaturation in the ring and are selected from the group consisting of:


23. The film adhesive according to claim 19 in which the independentelectron acceptor compound (iii) is selected from the group consistingof fumarates, maleates, acrylates, and maleimides.
 24. The film adhesiveaccording to claim 19 in which the independent electron acceptorcompound (iii) is a bismaleimide selected from the group consisting ofN,N′-ethylene-bis-maleimide, N,N′-butylene-bis-maleimide,N,N′-phenylene-bis-maleimide, N,N′-hexamethylene-bis-maleimide,N,N′4,4′-diphenyl methane-bis-maleimide, N,N′-4,4′-diphenylether-bis-maleimide, N,N′-4,4′-diphenyl sulfone-bis-maleimide,N,N′-4,4′-dicyclohexyl methane-bis-maleimide,N,N′-xylylene-bis-maleimide, and N,N′-diphenylcyclohexane-bis-maleimide.